A ‘biorefinery’ concept sustainably produces both fuels and chemicals from bio feedstock therefore are being matured for implementation in near future. In the first decade of 21st century, much research has been focused on developing new catalytic routes for the conversion of several bio based platform molecules into multiple commodity products. The presence of oxygen containing multiple functional groups, makes the bio derived molecules unique as well as they require number of processing steps as compared to the fossil derived hydrocarbons.
In 21st century oil refineries industries focused on analogous of bio-refineries to produce fuel and specialty chemicals due to shortage of fossil resources. Thus, green catalytic chemistry community is currently trying to develop new platform chemicals based on biomass as a starting material for chemical and fuel. The lignocellulosic material, which is derived from biomass is becoming one of the primary starting compound for sustainable chemistry. It can be converted by different means to a variety of compounds, such as hydrolysis to levulinic acid (LA), furfural, lactic acid etc. The new generation abundantly available lignocellulosic feedstock at lower cost can be easily converted to a variety of starting materials. For ex. hydrolysis of 5-hydroxymethyl furfural gives levulinic acid (LA) and processes have been already developed from wood, cellulose etc.
In recent years, the concept of bio-refineries similar to oil refineries is being considered so that the process economics for biofuel will be more advantageous. γ-Valerolactone (GVL) is considered a very interesting green, bio-based platform chemical with high application potential. Chemically, γ-Valerolactone is 5-Methyldihydrofuran-2(3H)-one having structural formula given below. This clear liquid is one of the more common lactones. It is a structural isomer of delta-valerolactone.

Levulinic acid (4-Oxopentanoic acid) is a keto acid and is a white crystalline compound soluble in water, ethanol, and diethyl ether.

Hydrogenation and subsequent cyclization of levulinic acid, either by using homogeneous or heterogeneous catalysts to γ-Valerolactone are reported in the prior arts.
Joo et al. demonstrated the use of water soluble homogeneous ruthenium catalysts with sulfonated triphenylphosphine ligands (e.g. HRuCl(Dpm)3, Dpm=diphenylphosphinobenzene-m-sulfonic acid) for the hydrogenation of oxo- and unsaturated acids. However, catalyst activity for the hydrogenation of keto-acids like LA was low. Recently, Horv' ath and co-workers reported the use of Ru(Acac)3 in combination with TPPTS (tris(3-sulfonatophenyl)phosphine) for the hydrogenation of LA in water at 140° C. and 69 bar hydrogen. After 12 h, LA conversion was complete and GVL was obtained in essentially quantitative yield (>95%). Although most hydrogenations have been performed with molecular hydrogen in presence of heterogeneous catalysts, Haan et at. 22 showed that the hydrogenation of LA or ethyllevulinate to GVL using formic acid as the hydrogen donor with a variety of heterogeneous catalysts. But reactions were carried out in the gas phase system at 200-350° C. and pressure between 1-10 bar. The maximum yield was 81 mol % in case of ethyl levulinate as the substrate.
US2010217038 discloses a process for conversion of levulinic acid into pentanoic acid, the process comprising (a) hydrogenating levulinic acid in presence of hydrogen with a non-acidic heterogeneous hydrogenation catalyst comprising a hydrogenation metal supported on a solid catalyst carrier to obtain a first effluent comprising gamma valerolactone; (b) contacting at least part of the first effluent under hydrogenating conditions, in the presence of hydrogen, with a strongly acidic catalyst and a hydrogenation metal to obtain a second effluent comprising pentanoic acid and unconverted gamma valerolactone, and wherein part of the unconverted gamma valerolactone is recycled to step (a) and/or step (b).
US2004254384 relates to a process for producing 5-methyl-dihydro-furan-2-one from levulinic acid in presence of a supercritical fluid, and in presence of optionally-supported metal catalyst selected from the group consisting of palladium, ruthenium, rhenium, rhodium, iridium, platinum, nickel, cobalt, copper, iron, osmium, compounds thereof, and combinations thereof.
US 2003055270 relates to a process for producing 5-methylbutyrolactone from levulinic acid utilizing an optionally supported metal catalyst selected from the group consisting of carbon, SiO2, and Al2O3. The catalyst has both a hydrogenation and a ring-closing function. The metal catalyst of the invention can be selected from the group consisting of Group VII (Groups 8-10) of the Periodic Table of Elements, preferably selected from the group consisting of iridium, palladium, platinum, rhenium, rhodium and ruthenium and combinations thereof.
An article titled “Synthesis of γ-Valerolactone by Hydrogenation of Biomass-derived Levulinic Acid over Ru/C Catalyst”, by Zhi-pei Yan et. al., published in Energy & Fuels, Vol. XXXX, discloses the applicability of Ru/C catalyst in the hydrogenation of LA to GVL.
Article titled “Catalytic synthesis of α-methylene-γ-valerolactone: a biomass-derived acrylic monomer” by Leo E Manzer et.al in Applied Catalysis A: General Volume 272, Issues 1-2, 28 Sep. 2004, Pages 249-256 discloses a two-step process for its synthesis from a biomass-derived starting material, levulinic acid. The first step is a high yield hydrogenation of levulinic acid to γ-valerolactone (GVL) in nearly quantitative yield using a Ru/C catalyst. The second step is a heterogeneous, gas phase catalytic condensation of formaldehyde with GVL over basic catalysts, prepared from Group 1 and 2 metal salts on silica. The said article further states that, the described process however suffers from rapid catalyst deactivation but proper choice of the catalyst provides a thermodynamically unfavorable yet desired product in good yield.
The homogeneous catalyst systems used in the hydrogenation process obviously have serious drawbacks of catalyst recovery and its recycle and multistep synthesis of ligands, thus not favorable for commercial application. Serious problem of active metal leaching/deactivation of the heterogeneous catalyst in hydrogenation of LA is also observed and reported by Lange et. al. Although carbon supports overcome the problem of leaching to some extent however do not allow for the regeneration of deactivated catalyst by coke burn-off.
Further, the reported methods which use noble metals are neither sustainable nor low-priced and has major problem of tedious operating condition, which causes serious environmental problems as well as suffers from the drawback of poor selectivity of the desired product and corrosive nature of reagents. With view to overcome the drawbacks in the use of noble metals for the hydrogenation of levulinic acid and subsequent cyclization to γ-valerolactone, it is the object of the present invention to provide a process for complete selectivity to γ-valerolactone using cost effective, efficient, non-noble catalysts.